So far, an engine equipped with a supercharger such as a turbocharger has been provided with an exhaust bypass passage for bypassing a turbine of the supercharger, and the exhaust bypass passage has been provided with a waste gate valve for opening and closing the exhaust bypass passage. Upon opening/closing of the waste gate valve, an excessive rise in a boost pressure is suppressed, whereby stability of the boost pressure is ensured, and damage to the engine or the supercharger itself is inhibited.
In recent years, moreover, it has been common practice to actively control the opening/closing action of the waste gate valve in accordance with the operating state of the engine. There has been, for example, a supercharger-equipped engine having a first fuel injection valve for injecting fuel to an intake path (intake port) (i.e., port injection valve), and a second fuel injection valve for injecting fuel into a combustion chamber (i.e., cylinder injection valve), wherein in accordance with the operating state of the engine, the cylinder injection valve and the port injection valve are controlled, and a waste gate valve (exhaust bypass valve) is also opened and closed as appropriate (see, for example, Patent Document 1).
This Patent Document 1 discloses a technology which opens the exhaust bypass valve together with an intake bypass valve, for example, when shifting from a homogeneous lean operation concurrently using supercharging to stratified combustion involving no supercharging.